1. Field of the Invention
The present invention relates generally to method and apparatus for removing pollutants from contaminated soil and, more particularly, to a method and apparatus for removing pollutants from contaminated soil in which the soil is first purified from coarse constituents by screening or crushing and then subjected to extraction with washing water mixed with additives, after which the soil is separated from the washing water and additionally rinsed with rinsing water, whereupon the rinsing water is freed in a purification process from the pollutants extracted from the soil.
2. Description of the Prior Art
A method for decontaminating soil is described in European Patent Application 84 730 152.0, publication number 0 185 831. The prior-art methods, including European Publication number 0 185 831, can theoretically remove nearly all pollutants from soil. In practice, however, there are important and serious limitations to these methods since the soil constituents having a particle size ranging from 0 to 10 or 20 .mu.m mostly have a laminar structure and, owing to the large outer and inner surface area, have a high absorption capacity for pollutants. High-boiling solid pollutant carriers such as tar, asphalt and coal sometimes coagulate with grains of quartz or other soil constituents and, like wood, charcoal and other mainly organic pollutant carriers, have a large internal surface area and are present in virtually all contaminated soil. Even when large amounts of mechanical energy are used, e.g., in the form of ultrasonic vibration or impacts, pollutants cannot be removed or dissolved from the soil in sufficient quantity by using water mixed with "eco-friendly" chemicals. The fine substances, therefore, have to be separated by wet or dry sorting and, in the case of wet separation, have to be concentrated and dewatered, so that they continue to be in the form of a waste material which requires additional specialized treatment. The organic pollutant carriers (low-density materials), which usually form coagulations with quartz having a density of less than 1.6 kg/dm.sup.3, are thus dissolved or separated only in small proportions according to existing methods.
It is, therefore, an object of the present invention to provide an improved method for decontaminating soil whereby contaminated soil can be freed from pollutants in a technically and economically acceptable manner even when the soil contains very fine solid constituents having a laminar structure and a particle size usually below 20 .mu.m and also contains high-boiling pollutants and pollutant carriers (low-density materials).
Still other objects and advantages of the present invention will become apparent in light of the attached drawings and written description of the invention presented herebelow.